2. The structural ring interconnect printed circuit board assembly of
claim 1 further comprising at least one connector on a surface of the
printed circuit board.

3. The structural ring interconnect printed circuit board assembly of
claim 2, wherein the at least one connector comprises at least one socket
connector on a surface of the printed circuit board.

4. The structural ring interconnect printed circuit board assembly of
claim 3, wherein the at least one connector further comprises at least
one servo socket connector on a surface of the printed circuit board.

9. The structural ring interconnect printed circuit board assembly of
claim 7, wherein the printed circuit board is attached to and supported
by a plurality of v-blocks contained in the airframe skirt.

10. The structural ring interconnect printed circuit board assembly of
claim 9, wherein one of the at least one socket connector is a power
supply socket.

11. The structural ring interconnect printed circuit board assembly of
claim 10, further comprising a radio socket connector on a surface of the
printed circuit board.

16. A structural ring interconnect printed circuit board assembly for a
ducted fan unmanned aerial vehicle comprising:a plurality of printed
circuit boards attached to a core vehicle body, wherein each of the
plurality of printed circuit boards conforms to the shape of the airframe
skirt of the core vehicle body, wherein each of the plurality of the
printed circuit boards provides structural integrity to the core vehicle
body.

17. The structural ring interconnect printed circuit board assembly of
claim 16, wherein the arc length of each of the plurality of printed
circuit boards extends between 45 and 90 degrees around the circumference
of the airframe skirt.

18. The structural ring interconnect printed circuit board assembly of
claim 17, wherein the inner and outer duct walls of the airframe skirt
are thicker in sections of the airframe skirt in spaces between each of
the plurality of printed circuit boards.

19. The structural ring interconnect printed circuit board assembly of
claim 18 further comprising at least one connector on a surface of each
of the plurality of printed circuit boards.

20. The structural ring interconnect printed circuit board assembly of
claim 19, wherein the at least one connector comprises at least one
socket connector on a surface of the printed circuit board.

Description:

BACKGROUND OF THE INVENTION

[0002]In aerospace applications, it is typical to use wire harnesses as
interconnects in electrical systems. However, these harnesses are often
bulky, heavy, costly to build and maintain, and subject to corrosion and
other defects. Further, with the advent of modular ducted fan unmanned
aerial vehicles (UAVs), the ducted wing is comprised of multiple pods
that require a system allowing for quick disconnect and replacement of
pods around the circumference of a core vehicle. Particularly with
respect to micro-air vehicle UAVs, the wire harness configuration and
resultant connectors are cumbersome and weigh too much when placed around
the circumference of the duct to connect to each pod. These wire
harnesses do not provide structural integrity to the UAV and additional
material must be used to thicken walls and bulkheads, for example, to
provide such support. This additional material necessarily adds more
weight to the UAV assembly. In addition, the wire harnesses are
frequently modified at a significant cost to accommodate changes in these
various pods.

[0003]Printed circuit boards (PCBs), on the other hand are rugged,
inexpensive, and highly reliable. PCBs provide both the physical
structure for mounting and holding electronic components as well as the
electrical interconnection between components. A PCB consists of a
non-conducting substrate, known as prepreg, upon which a conductive
pattern or circuitry is formed. The most common type of prepreg is
fiberglass with epoxy resin. Prepreg is available in different styles
with varying amounts of resin and glass fibers, which allows the
manufacturer to control the thickness between the layers and to provide
the appropriate amount of resin flow between circuitry. Copper is the
most prevalent conductor, although nickel, silver, tin, tin-lead, and
gold may also be used as etch resists or top-level metal. Multilayer PCBs
consist of alternating layers of conductor and insulating material bonded
together. The conductive layers are connected by plated through-holes,
which are also used to mount and electrically connect components. PCBs
may be either rigid, flexible, or a combination of the two known as a
rigid-flex.

SUMMARY OF THE INVENTION

[0004]PCBs are employed most often as backplanes or motherboards in
standard home computers, which is essentially a large circuit board that
contains sockets for expansion cards. These former PCBs were simply
delicate components in an operating system that played no role with
regard to the overall structural integrity of the device. In the present
invention, the backplane is specifically designed to provide structural
integrity to the UAV. For example, the backplane's edges are contoured to
fit the shape of the core vehicle's outer shell and the backplane is
integrated into the UAV to prevent warping of the core body due to
bending moments. The backplane also provides a lightweight surface to
bear the weight of the pods that join together to form the UAV's duct.
Further, the use of the multilayer PCB in a ducted fan UAV allows for
impedance matching and offers electromagnetic interference shielding for
conductors. In addition, the backplane of the present invention allows
straightforward redesigns to accommodate various pods, which would be
inexpensive and quick compared with wire harness redesign.

[0007]In a second aspect, the present invention provides a structural ring
interconnect printed circuit board assembly for a ducted fan unmanned
aerial vehicle that comprises a plurality of printed circuit boards
attached to a core vehicle body, wherein each of the plurality of printed
circuit boards conforms to the shape of the core vehicle body's airframe
skirt, and wherein each of the plurality of the printed circuit boards
provides structural integrity to the core vehicle body.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]FIG. 1A is a perspective view of the structural ring interconnect
printed circuit board, v-blocks, and the airframe skirt prior to
attachment according to one embodiment.

[0009]FIG. 1B is a perspective view of the v-blocks in place within the
airframe skirt prior to attaching the structural ring interconnect
printed circuit board assembly according to one embodiment.

[0010]FIG. 1c is a perspective view of the structural ring interconnect
printed circuit board assembly after attachment to the airframe skirt and
v-blocks according to one embodiment.

[0011]FIG. 2A is a top view of the printed circuit board according to one
embodiment.

[0012]FIG. 2B is a bottom view of the printed circuit board according to
one embodiment.

[0013]FIG. 3A is a perspective view of the structural ring interconnect
printed circuit board connected to a pod containing printed circuit
boards with card-edge connectors according to one embodiment.

[0014]FIG. 3B is a perspective view of the structural ring interconnect
printed circuit board separated from a pod containing printed circuit
boards with card-edge connectors according to one embodiment.

[0015]FIG. 3c is a perspective view of the structural ring interconnect
printed circuit board connected to a pod with a printed circuit board and
connectors attached on the pod's bottom side according to one embodiment.

[0016]FIG. 3D is a perspective view of the structural ring interconnect
printed circuit board separated from a pod with a printed circuit board
and connectors attached on the pod's bottom side according to one
embodiment.

[0018]As used herein, a printed circuit board (PCB) 12 provides the
physical structure for mounting and holding electronic components as well
as the electrical interconnection between components. The PCB 12 consists
of a non-conducting substrate, known as prepreg, upon which a conductive
pattern or circuitry is formed. The most common type of prepreg is
fiberglass with epoxy resin. Prepreg is available in different styles
with varying amounts of resin and glass fibers, which allows the
manufacturer to control the thickness between the layers and to provide
the appropriate amount of resin flow between circuitry. Copper is the
most prevalent conductor, although nickel, silver, tin, tin-lead, and
gold may also be used as etch resists or top-level metal. Multilayer PCBs
consist of alternating layers of conductor and insulating material bonded
together. The conductive layers are connected by plated through-holes,
which are also used to mount and electrically connect components. PCBs 12
may be either rigid, flexible, or a combination of the two known as a
rigid-flex.

[0019]As used herein, a core vehicle body 14 is the unitary portion of the
ducted fan UAV, shown in FIGS. 1a-1c. Pods 18 connect to the core vehicle
14 to form a complete duct on a UAV. As used herein, pods 18 are
streamlined, detachable housings that may contain various payloads, such
as weapons or fuel. The arrangement of the various pods 18 relative to
one another is limited only by the location of the connectors 20 on the
core vehicle 14, the desired center of gravity, and other basic operating
parameters.

[0020]As used herein, the airframe skirt 16 of the core vehicle body 14
forms the lower portion of the duct on a UAV, shown in FIGS. 1a-1c. The
airframe skirt 16 is preferably substantially v-shaped such that when a
pod 18 is connected to the airframe skirt 16 the profile or cross-section
of the resulting duct is in accordance with standard streamlined profiles
known in the art. As shown in FIGS. 1a-1c, the inner wall 22 of the
airframe skirt is typically taller than the outer duct wall 24 of the
airframe skirt. As detailed below, the PCB 12 is inserted onto and/or
into the airframe skirt 16 at the opening of the top of the "V" and is
attached to the airframe skirt 16 via screws, rivets, glue, or a
combination of these, for example, or by any other attachment means known
in the art. The PCB 12 is preferably mounted within the airframe skirt
16. Alternatively, the PCB 12 may be mounted on top of the airframe skirt
16, which would generally be used for those embodiments in which the PCB
12 is a single layer or multilayer that is still relatively thin such
that a smooth transitional surface is provided between the pods 18 and
the airframe skirt 16. In another embodiment the PCB 12 may contain one
or more layers that rest on top of the outer duct wall 24 of the airframe
skirt 16 coupled with one or more PCB layers that fit within the airframe
skirt 16, essentially providing a PCB 12 with a top lip (not shown)
running along the PCB's outer edge 28. This outer lip would aide in
alignment of the PCB 12 with the airframe skirt 16 prior to and during
attachment.

[0021]As used herein, the PCB 12 conforms to the shape of the airframe
skirt 16 of the core vehicle body 14 such that the PCB's inner and outer
edges 26, 28 are contoured to substantially mate with both sides of the
airframe skirt's v-shell 16 along the PCB's entire arc length. With
respect to the layer or layers of PCB that rest on top of the airframe
skirt 16, the PCB's outer edge 28 substantially matches the outer
perimeter of the outer duct wall 24 of the airframe skirt 16 to create a
smooth transition between the two, while the PCB's inner edge 26
essentially abuts the inner wall 22 of the airframe skirt 16. With
respect to the layer or layers of PCB that rest within the airframe skirt
16, the PCB's outer edge 28 essentially abuts the outer duct wall 24 of
the airframe skirt 16, while the PCB's inner edge 26 essentially abuts
the inner wall 22 of the airframe skirt 16. Therefore, embodiments using
multilayer PCBs 12 require that the shape of the PCB 12 will taper
according to the aerodynamic taper of the airframe skirt 16. By
configuring the PCB 12 in this manner, the outer and inner walls 24, 22
of the airframe skirt 16 are reinforced and they can better resist
bending moments. The PCB 12 also provides structural stability so that a
major component, like the engine, can be mounted to the inner wall 22 of
the airframe skirt 16.

[0022]In one embodiment, the structural ring interconnect printed circuit
board assembly 10 further comprises at least one connector 20 on a
surface of the printed circuit board 12, shown in FIGS. 2a-2b. As used
herein, the at least one connector 20 may comprise a socket connector, a
servo connector, a maintenance connector, or other type of connector
known in the art. A connector 20 may be located on the top or bottom
surface of the PCB 12 or act as an edge connector ninety degrees lateral
to the PCB 12.

[0023]In one embodiment, the at least one connector 20 comprises at least
one socket connector 30 on a surface of the PCB 12, shown in FIG. 2A. The
at least one socket connector 30 may interact with a complementary
connector on a PCB 12 that is attached either to a pod 18, shown in FIGS.
3a-3d, or to a vertical routing channel contained within a mechanical
strut contained in the airframe skirt 16.

[0024]In one embodiment, the at least one connector 20 further comprises
at least one servo socket connector 32 on a surface of the PCB 12, shown
in FIG. 2B. The at least one servo socket connector 32 interacts with a
complementary connector on a servo motor to control flight direction by
manipulating the UAV's vanes.

[0025]In one embodiment, the PCB 12 comprises a plurality of layers. The
appropriate number of PCB layers is based on the specific structural
need, for example, the weight of the vehicle payload or size of the UAV.
The exact number of layers can be calculated by performing a vehicle
structural analysis using techniques known in the art.

[0026]In one embodiment, one or more of the plurality of layers is a
ground plane to shield conductors from electromagnetic interference.

[0027]In one embodiment, the arc length of PCB 12 extends at least 180
degrees around the circumference of the airframe skirt 16, shown in FIGS.
2a-2b. The inner and outer walls 36, 34 of the airframe skirt 16 that do
not contain or do not abut the PCB 12 can be thickened with a lightweight
material, such as a carbon fiber composite, to maintain the vehicle's
structural rigidity. Under this embodiment, the PCB 12 still remains a
lighter weight alternative to wire harnesses and structural rigidity is
still achieved.

[0028]In one embodiment, the arc length of the PCB 12 extends 360 degrees
around the circumference of the airframe skirt 16, shown in FIGS. 1a-1c.

[0029]In one embodiment, the PCB 12 is attached to and supported by a
plurality of v-blocks 38 contained in the airframe skirt 16, as shown in
FIGS. 1a-1b. As used herein, the v-blocks 38 are lightweight supports or
placeholders on which the PCB 12 rests during and after assembly. The PCB
12 may be attached to the v-blocks 38 via glue or screws 48, for example,
or alternatively, the v-blocks 38 may simply act as passive supports
while the PCB is attached to the walls of the airframe skirt. The
v-blocks 38 may be formed as part of the molding of the airframe skirt
16. Alternatively, the v-blocks 38 may be separate components placed
within the airframe skirt. Regardless of whether the v-blocks 38 are
molded as part of the airframe skirt or are separate components, the
v-blocks 38 are considered to be part of the core vehicle body 14. The
v-blocks 38 extend from the point where the inner and outer duct wall
meet and fuse together up toward the opening of the airframe skirt's "V."
The exact height of the v-blocks 38 is dictated by the thickness and
number of layers of the PCB 12.

[0030]In one embodiment, one of the at least one socket connector 30 is a
power supply socket 40, as shown in FIG. 2A. As used herein, the power
supply socket 40 may interact with a complementary connector attached to
a pod 18 or to a power filter housing residing in the airframe skirt 16.

[0031]In one embodiment, the structural ring interconnect printed circuit
board assembly 10 further comprises a radio socket connector 42 on a
surface of the PCB 12, as shown in FIG. 2B. As used herein, the radio
socket connector 42 may interact with a complementary connector attached
to a radio.

[0032]In one embodiment, the structural ring interconnect printed circuit
board assembly 10 further comprises an antenna coaxial cable connector 44
on a surface of the PCB 12, as shown in FIG. 2B. As used herein, the
antenna coaxial cable connector may interact with a complementary
connector attached to an antenna 46.

[0033]In one embodiment, the PCB 12 is either rigid or rigid-flex. As used
herein, the standard fiberglass material used in PCB rigid or rigid-flex
may be tailored for a UAV's specific structural need based on a vehicle
structural analysis conducted according to known techniques. In order to
incorporate additional strength, a layer of carbon fiber can be added to
the PCB 12 or carbon fiber can be added directly into the prepreg
material.

[0034]In one embodiment, the PCB's prepreg material is FR-4. FR-4, an
abbreviation for Flame Retardant 4, is a type of material used for making
a PCB 12. FR-4 describes the board itself with no copper covering. The
FR-4 used in PCBs 12 is typically UV stabilized with a tetrafunctional
epoxy resin system. FR-4 is typically a yellowish color. FR-4 that is
manufactured strictly as an insulator (without copper cladding) is
typically a difunctional epoxy resin system and a greenish color. FR-4 is
similar to an older material called G-10. G-10 lacked FR-4's
self-extinguishing flammability-characteristics. FR-4 has widely replaced
G-10 in most applications. Some military applications where destruction
of the circuit board is a desirable trait will still utilize G-10.

[0035]A PCB 12 needs to be an insulator to avoid shorting the circuit,
physically strong to protect the copper tracks placed upon it, and to
have certain other physical electrical qualities. FR-4 is preferred over
cheaper alternatives such as synthetic resin bonded paper due to several
mechanical and electrical properties; it is less lossy at high
frequencies, absorbs less moisture, has greater strength and stiffness
and is highly flame resistant compared to its less costly counterpart.
FR-4 is widely used to build high-end consumer, industrial, and military
electronic equipment and is also ultra high vacuum (UHV) compatible.

[0036]In one embodiment, the ground plane is a carbon fiber skin
composite.

[0037]As used herein, all the foregoing descriptions and embodiments with
respect to the first aspect are equally applicable to the following
second aspect as well. Furthermore, all embodiments disclosed for each
aspect may be combined with other embodiments.

[0038]In a second aspect, the present invention provides a structural ring
interconnect printed circuit board assembly 10 for a ducted fan unmanned
aerial vehicle that comprises a plurality of printed circuit boards 12
attached to a core vehicle body 14, wherein each of the plurality of
printed circuit boards 12 conforms to the shape of the airframe skirt 16
of the core vehicle body 14, and wherein each of the plurality of the
printed circuit boards 12 provides structural integrity to the core
vehicle body 14.

[0039]As used herein, the plurality of PCBs 12 are spaced around the
circumference of the airframe skirt 16 based on the specific UAV needs.
The plurality of PCBs 12 may combine to form a 360 degree PCB 12 or may
alternatively contain spaces in between. Where there are spaces between
the plurality of PCBs 12, the inner and outer walls 36, 34 of the
airframe skirt that do not contain or do not abut a PCB 12 can be
thickened with a lightweight material, such as a carbon fiber composite,
to maintain the vehicle's structural rigidity. Under this embodiment, the
PCB 12 still remains a lighter weight alternative to wire harnesses and
structural rigidity is still achieved.

[0040]In one embodiment, the arc length of each of the plurality of PCBs
12 extends between 45 and 90 degrees around the circumference of the
airframe skirt 16.

[0041]In one embodiment, the inner and outer duct walls 36, 34 of the
airframe skirt 16 are thicker in sections of the airframe skirt 16 in
spaces between each of the plurality of PCBs 12.

[0042]In one embodiment, the structural ring interconnect printed circuit
board assembly 10 further comprises at least one connector 20 on a
surface of each of the plurality of PCBs 12.

[0043]In one embodiment, the at least one connector 20 comprises at least
one socket connector 30 on a surface of the PCB 12. The at least one
socket connector 30 may interact with a complementary connector on a PCB
12 that is attached either to a pod 18 or to a harness route channel,
such as a stator or engine mounting strut contained in the airframe skirt
16.